High Tg Epoxy Varnish for Pad Cratering Resistance
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Solution Overview
Problem
Printed circuit boards suffer from pad cratering due to mechanical stress between the resin and copper, leading to dislodged chips and surface damage, which existing laminates and prepregs fail to adequately address.
Innovation Solution
Development of varnish compositions comprising a mixture of epoxy resins, including bisphenol-A novolac epoxy resins, multi-functional, and bifunctional epoxy resins, with specific weight ratios and hardeners, that produce high TMA Tg laminates, reducing mechanical stress and improving thermal and mechanical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high Tg laminates are made using conventional varnish ingredients, then thermal properties are improved, but manufacturing cost increases
Solution Approach 1:
The patent uses a composite epoxy resin system combining multiple epoxy resins (including bisphenol-A novolac epoxy resin and other epoxy resins) in specific weight ratios to achieve high Tg properties. This composite approach allows the formulation to reach exceptional Tg values while avoiding the need for expensive conventional high-Tg varnish ingredients, thus resolving the contradiction between thermal performance and manufacturing cost.
Solution Approach 2:
The patent systematically varies the composition parameters of the epoxy resin system, specifically the weight ratios of different epoxy resins and the selection of hardeners, to optimize Tg achievement. By adjusting these compositional parameters, the formulation achieves high Tg values through cost-effective raw material combinations rather than relying on expensive conventional ingredients.
2Reliability
If mechanical stress between resin and copper is reduced, then pad cratering is prevented, but laminate performance requirements become more difficult to meet
Solution Approach 1:
The patent modifies the chemical composition parameters of the resin system by selecting specific epoxy resin types and hardeners that provide both low mechanical stress and high thermal performance. This dual-optimization approach allows the laminate to simultaneously achieve pad cratering resistance and meet stringent performance requirements without increasing device complexity.
Solution Approach 2:
The composite epoxy resin system with specific component ratios creates a balanced material properties profile that reduces mechanical stress between resin and copper while maintaining or enhancing overall laminate performance. This composite formulation approach resolves the contradiction by providing a material that satisfies both reliability and performance requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The varnish compositions result in prepregs and laminates with unexpectedly high Tg values, exceeding 280°C, and extended thermal stability, significantly reducing the incidence of pad cratering while maintaining economic viability.
Implementation Method 1
varnish compositions comprising a mixture of epoxy resins, including bisphenol-A novolac epoxy resins, multi-functional, and bifunctional epoxy resins, with specific weight ratios and hardeners
Data Source
AI summary
Varnish compositions and prepregs and laminates made therefrom wherein the varnish compositions include at least one first epoxy resin and at least one second epoxy resin that includes a bisphenol-A novolac epoxy resin and a harder wherein the at least one first epoxy resin and the at least one second bisphenol-A novolac epoxy resin are present in the varnish at a weight ratio ranging from about 1:1 to about 1:3.